In the electronic sensing market, there are a wide variety of sensors for sensing objects at a given location. Such sensors are configured to sense detectable and/or measurable characteristics of an object in order to sense presence of an object near or about the sensor and other features and characteristics of the object being sensed. Such “sense characteristics” may include a variety of detectable characteristics, such as electronic, electromagnetic, ultrasonic, thermal, optical, etc. characteristics.
Sensors may be configured to passively detect characteristics of an object, by measuring parameters such as temperature, weight, or various emissions such as photonic, magnetic or atomic emissions of an object in close proximity or contact with the sensor. An example of this is a non-contact infrared thermometer that detects the black body radiation spectra emitted from an object, from which its temperature can be computed.
Other sensors work by directly exciting an object with a stimulus such as voltage or current, then using the resultant signal to determine the physical or electrical characteristics of an object. An example of this is a fluid detector consisting of two terminals, one that excites the medium with a voltage source, while the second measures the current flow to determine the presence of a conductive fluid, such as water.
Other sensors operate by capacitance and include an arrangement of electrodes that form an array of capacitive elements. For example, certain fingerprint sensors comprise a first group of conductors (e.g., conductive traces or lines) arranged in a side-by-side configuration and a second group of conductors (e.g., conductive traces or lines) arranged in a side-by-side configuration, wherein the second group of conductors transversely overlaps the first group of conductors and is separated from the first group of conductors by a dielectric. A capacitive sensing element is formed at each overlap, and the impedance at each overlap is sensitive to the nature of an object contacting or nearby the sensing element.
Recent efforts have been made to incorporate sensors into flat panels of host devices. For example, efforts have been made to incorporate capacitive finger print sensors into devices such as smart phones and tablet computers by incorporating that sensor into a glass panel, such as a display and/or interface panel of the device. Such sensors should be dimensionally stable so that they do not expand or contract differentially with respect to the glass panel, and the panel should have a smooth, continuous outer surface, even in the vicinity of the sensor. In addition, it is a challenge to incorporate the conductive sensing elements and interconnecting conductors in a small portion of a continuous panel, which may be necessary to fabricate a cost-effective sensor.